Lamp and automobile headlight



Sept. 18, 1934. .5 CHRI TMAS I 1,974,388

LAMP AND AUTOMOBILE HEADLIfil-IT].

Filed May 26. 195;. 2- Sh'ets-Shee't' 1 M ATTORNEY Sept. 18, 1934. a CHRISTMAS 1,974,388 I v LAMP AND AUTOMOBILE HEADLIGHT Filed May 26, 1931 2 Sheets-Sheet 2 IN VEN TOR.

Patented Sept. 18, 1934 llNlTED STATES PATENT OFFICE LAMP AND AUTOMOBILE HEADLIGHT Burton Christmas, Pittsburgh, Pa.

Application May 26, 1931, Serial No. 540,030

3 Claims.

bright headlights has arisen from their failure.

to furnish satisfactory lighting in a fog. The device of the present inventionenables these and other difficulties to be overcome.

According to the form ofthe invention herein disclosed anordinary parabolic reflector may be provided with a suitable incandescent lamp at its focus,,but the bulb of the lamp is shown as prolight for lighting the road which spreads fan like horizontally or downwardly emanating rays. Thus the road is illuminated on both sides and more uniformly than has hitherto been possible. 7 At the same time, the cutting off of the light rays which would go upward, even at a slight diagonal, has cut off the rays which make a bright layer in a fog in front of the driver's eyes and has confined the rays to a space near the ground which is usually nearly free from fog. Other features and advantages will hereinafter appear.

In the accompanying drawings:

Figure 1 is a side view of a vertical section through a reflector and showing the bulb in place.

Figure 2 is aside view of the bulb on a larger scale.

Figure 3 is an end view of the parts seen in Figure 2.

Figure 4 is a top view of Figure 2.

Figure 5 is a horizontal section view from above.

Figure 6 is a horizontal section of a reflector showing the bulb in place, and

Figure '7 is a front'view of the bulb in the reflector showing the darkened area near the bottom of the reflector from which no light comes.

A bulb 10 is supported by any desired focusing mount, not shown, in a parabolic reflector 11, of

- an automobile headlight. For distributing the light coming from the filament more uniformly 55 than has hitherto proved possible, the bulb inthe parts seen in cludes flat panels or ribs 12, which run vertically around the outer end 13 of the bulb 10 each made by flattening out the slight curvature of the bulb surface, so that it reflects back in the same general direction a beam of more nearly 0 parallel instead of converging rays. As a result the vertical center panels 14, reflect considerable of the light, almost directly back to the parabola 11. The adjacent side panels 15 and 16, also reflect light back mainly, diagonally to the parabola 11, and the side panels, 1'7, beyond these are successively at greater angles and therefore re-' flect more of the light and also reflect it further to one side or the other of the center line of the parabola. Since the panels run vertically they spread the light from the filament 18, 'in a direction which is generally horizontal and. is fan like; Moreover," since all the panels are beyond the focus of the parabola they tend to spread the light sideways instead of sending it directly forward, thus illuminating a wide stretch of roadway in front of the car and illuminating that stretch more uniformly than has hitherto been found possible. It is well known that even the most transparent glass reflects back part of the light 30 which strikes its surface instead of transmitting that light, the percentage of reflected light reaching eight per cent as a minimum for light impinging vertically, and rapidly increasing when I the light impinges at other angles. As a result 35 of the oblique angle at which most of the light from the filament l8 strikes the upper and lower parts, 18', of the side panels 15, 16 etc., most of that light is ultimately reflected horizontally fanwise instead of passing up or down clear of the g0" parabolic reflector 11, as is usual and which hitherto has resulted in a loss of the light. In fact, the light which rises upwards shines so brightly in a fog at the front of the automobile, that it blinds the eye of the automobile driver to what is beyond the shining fog at the front of the automobile. Thus, the present invention provides means by which light, would otherwise be lost or which is a handicap on the driver, may be utilized to evenly illuminate the road.

Silvering the bulb end may also cause the bulb to reflect back the whole of the light which would directly strike any eye standing in front of the parabolic mirror. In addition to silvering the end of the bulb it is found advantageous to cut off a part of the light which ordinarily goes from the filament to the lower part of the parabolic mirror because that light is generally reflected slightly upward, blinding the eyes of the person facing the headlight. For this purpose there is illustrated a silver reflector 26 covering the round end of the bulb but with its edge inclined at an angle of 60 degrees or little more, the edge of the silvering lying in a plane which only just clears the end of the lower filament. This brings the top edge of the silvering on the bulb just far enough back along the bulb to cutoff any direct light rays from the filament which would escape diagonally upward in front of the parabolic mirror. In the form of the invention herein illustrated, there is no silvering at the bottom of the bulb, the silvering being shown as cut away almost in a half-moon, which in a satisfactory standard bulb was about a half-inch from point 20 to point 21, and has a maximum depth of about three-sixteenths of an inch from a line joining the points. The fiat ribs or panels 14, are shown as covering the same area as the silvering, terminating at the edge of the half-moon, while the side panels, 15 and 16 etc., terminate at the edge of the silvering of the bulb, described some distance above. The unsilvered half-moon 19, allows direct light from the filament 17, to fall on the bottom of the parabolic mirror, both behind the filament and up to a point directly below the lamp filament, but allows almost no light to reach the lower front part 22, of the parabolic mirronwith the result that the parabolic mirror is dark over an area 23, about an inch and a half wide and slowly narrowing, for the most part, practically up to the vertical sides, 24. As a result of this darkened area 23, and the bright area 25, behindit, it is found that the roadway is illuminated by a light which cannot blind a person of normal height standing in front of the automobile.

Having thus described certain embodiments of the invention, what is claimed is:

1. The combination with a headlight reflector having a parabolic mirror, of an electric bulb having a filament, glass walls on the bulb forming a smooth curve from the base outward, the

opposite end of the bulb having nearly fiat panels of substantial area running vertically and covering most of the end and conforming fairly closely to a smooth curve so as to reflect back into the parabolic mirror rays of light from the filament 80,

which spread horizontally, and a mirror covering the panels and terminating at their ends.

2. The combination with a headlight reflector having a parabolic mirror, of an electric bulb having a filament at the focus of the mirror and lying well back of the forward edges of the mirror, glasswalls on the bulb forming a smooth curve from the base outward to about a plane passing through the filament and cutting the mirror on all sides, the opposite end of the bulb having nearly flat panels of substantial area running vertically and covering all the area beyond the plane and conforming fairly closely to a smooth curve so as to reflect back into the parabolic mirror rays of light from the filament which spread horizontally, and a mirror covering the panels and terminating at their ends.

3. The combination with a headlight reflector having a parabolic mirror, of an electric bulb having a filament at the focus of the mirror and 100 lying well back of the forward edges of the mirror, glass walls on the bulb forming a smooth curve from the base outward to about a plane cutting the mirror near its front upper edge and passing through the filament, the opposite end of 195 the bulb having nearly fiat panels of substantial area running vertically and terminating at said plane except at the bottom, and an extension of the smooth curve between bottom panels forming-a smooth area below the filament so that undistorted light reaches the mirror from the bottom of the filament, and a mirror covering the panels and terminating at their ends.

BURTON 

